GE L30 Differential Problem (CT Polarity) 1

[rayas91]

Hi guys,

I just wanna ask a question to you.

I m at Power Plant and I m using L30 Line current differential relay.
I tried to energize the line and then It trips ,I did three times and gave me same result.
In relay software,there s no CT Polarity configuration , there s no even in manual.
I increased pickup setting from 0.2 to 0.3 and it never trips until now.There s no much load ,that s why i cant see the diff current yet.

I m cofused, Is it possible , because of CT polarity or somethingelse ?

Thanks ,

 

[DiscoP]

Incorrect CT polarity is often the cause of a false differential trip.

Other possible causes could be an incorrect phasing of the CT connections (or even a roll in the primary conductors), incorrect CT ratio tap connected - even shorts being left on CTs at one end.

Often the fault records from the relays will give you a good clue on what has happened.

 

[rayas91]

DiscoP

Thanks For Your Time,

I ve solved the problem , I just enabled the Line Charge Capacitance feature. And it didnt trip.

Polarity,CT Taps were ok.

Thanks.